The type of universal joint employing a fluid bearing with which the present invention is adapted to be used is described in LeFebre U.S. Pat. No. 3,698,192. Such a universal joint includes two members which are connected together in such a way that the relative angular orientation of the members with respect to each other can be varied. One of the members is provided with a receptacle means adapted to receive in spaced apart relation therefrom an annular plug element formed on the other member. A fluid supported membrane in the form of an annular tube or bladder filled with fluid acts as a rolling seal and is positioned between the periphery of the receptacle and the periphery of the plug. This fluid supported membrane enables the efficient use of the bearing under circumstances in which there is no axial load or in which there is an axial load component tending to move the two members apart or push them together. A characteristic of this type of universal joint is that a relatively low force is required to actuate the joint.
In the use of the foregoing type of universal joint, particularly when used as a load bearing joint and seal interposed between a movable nozzle and a fixed nozzle support in reaction motor systems employing movable nozzles for directional control, problems arise when changing axial movement to a side movement of the whole motor assembly. When the motor is turned, an angle orientation is effected which produces a tendency for the assembly to move sideways and pinch the bladder, which when repeated often enough, will destroy the bladder. This problem does not occur when the force is aligned axially.